1. Field of the Invention
The present invention relates to a pulse tube refrigerator, and more particularly, to a multi-stage pulse tube refrigerator.
2. Description of the Related Art
A pulse tube refrigerator is known as a refrigerator that generates cryogenic temperature. A pulse tube refrigerator generates cold at low-temperature ends of a regenerator tube and a pulse tube by repeating an operation of making a working gas (for example, helium gas), which is a working fluid compressed by a compressor, flow into the regenerator tube and the pulse tube and an operation of making the working fluid flow out of the pulse tube and the regenerator tube and recovering the working fluid to the compressor. Heat can be drawn from a cooling target by thermally contacting the cooling target at these low-temperature ends. In particular, a multi-stage multi-valve pulse tube refrigerator has characteristics of a high cooling efficiency and is expected to be applied to various fields.